Behavior based robotics systems grew out of a reactive approach to robot control in order to compensate for limitations (lack of state and inability to look into the past or the future) while conserving its strengths (real time responsiveness, scalability, and robustness). In the last decade, behavior based systems have proven themselves as one of the two favored general methodologies (the other being hybrid systems) for autonomous system control and as the most popular methodology for physical multi robot system coordination. Effective behavior selection or arbitration is a key challenge in behavior based control, as it determines which behavior or subset of behaviors controls the robot at a given time. Current systems run behaviors serially, but face myriad issues when given the task of running multiple behaviors at once that require overlapping resources of the robot.